The revelations over Peter Cruddas have put the spotlight back on party funding Photograph: Justin Williams/Rex Features

So many unsavoury rackets raise their grubby heads as a result of the latest Sunday Times sting on party funding (a deception justified in the public interest, Lord Justice Leveson please note) that it's hard to know where to start. But the biggest scam may be Tory fundraising wide boy Peter Cruddas's tape-recorded apparent promise of influence in return for donations from credulous punters. That's actually pretty bogus, a vanity sting for self-important people.

I won't say it doesn't happen occasionally. Rupert Murdoch's career is testimony to that, he must have swayed government policy in an important way four or five times over his baleful career as a British media mogul.

However, the best way to influence public policy is openly and through the front door, via perfectly legitimate representations made on behalf of companies – trades unions and charities too – in the traditional way, through MPs, civil servants and departmental ministers. If you own a newspaper and want the 50p tax rate cut (rich people think they CAN take it with them) you do so through the editorial columns you own. Ditto the campaign for a third runway at Heathrow: it's hardly a secret.

None of which is to make light of the Cruddas tapes. It's not his accent that matters (though it may have kept him away from Sam and Dave's private cheese on toast suppers in the No 10 flat), it's his attitude which reeks of casual impropriety. He crosses all sorts of red lines, offering access to what he calls the "policy committee" (policy unit?) as well as the No 10 flat, and appears to suggest that foreign donor money might illegally be laundered through Liechtenstein.

If it wasn't so serious, it would be funny. The would-be donors may be in the process of being stiffed in return for their fat cheques, but they think it's the real deal. The more vain among them probably think they're on the road to a knighthood or even a peerage, though most people have long since noticed that not having an honour nowadays is the greater honour.

Alas, poor Cruddas, he's made a great fortune as a posh bookie and he's giving buckets of money to charities (he helps poor kids, as he once was), but he's going to die a plain Mister too – along with anyone who ever wrote a "Pay David Cameron's party" cheque on Cruddas's invitation. Bliss!

There's also the question of Dave's sense of propriety, not to mention his attention span. As the Daily Mail – which will despise Cameron even more this week than it did last week – underlines today, it's not two years ago since David "Spotty" Rowlands, another City rich type from a modest background with a large fortune and a colourful reputation, was forced to resign as Tory treasurer over yet another scandal amid florid photos of his private life.

These blokes are supposed to be vetted by Andrew Feldman, an old Cameroon mate from their Oxford days, not to mention by hedge fund pioneer, Stanley Fink (Manchester Grammar and Cambridge), the slightly-less rich former treasurer who has had to take back this thankless task.

Why so careless? Perhaps because Cameron loves being PM but does not quite work hard enough at the more onerous side of the job, the details. Think the NHS reform bill. Think appointing Andy Coulson to No 10 – after the dear old Guardian privately warned him it would not be smart.

Needless to say, this makes Tony Blair look good (again) since Scotland Yard – the investigation led by the since discredited News International diner, John Yates – spent a year examining flakey allegations of loans-for-honours against him and his notably wholesome staff (dawn raids, lots of leaks and unwarranted publicity) without getting evidence like this.

It will be interesting to see how the Met handles the Liechtenstein angle this time. Remember the loans loophole in Labour's 2001 reform act (they didn't have to be declared) was spotted and first exploited by the Tories.

Sensible Labour politicians believe Yates would never have got the green light if the Tories had been in power. Remember that Margaret Thatcher and John Major went to Hong Kong expressly to raise money from rich Chinese in the late colonial era, business types who would help the British economy – and sterling – but also wanted the security of UK passports. Thatcher didmeet Murdoch prior to the purchase of the Times and Sunday Times in 1981-2, it emerged last week though the suspicions of people like me were denied at the time.

So none of this started with Cameron, Brown or Blair, as silly folk like Peter Oborne routinely assert. Before the first world war the Tories had a price list for honours. Cynical David Lloyd George, who escaped both insider trading and sex scandals before 1914 (and was thus available to win the war after 1916), merely made the system more efficient – as he had munitions manufacture.

Of course, all parties leaders hate having to engage in fundraising, grubby or otherwise. Where Thatcher and the old guard were more careful was in keeping the "Chinese walls" of separation between the blokes who raise the cash and write the cheques and the policy process: the PM was supposed not to know who had given what among the donors whom they met at both official and social events.

Slightly bogus too perhaps, you may argue. Yes and so is the tenuous link between knighthoods for "services to charity" (genuine ones) and donations to parties, which is also as old as the hills, but now discredited. But surely better than Peter Cruddas doing a bit of rough diamond business for the benefit of a couple of Sunday Times reporters. He sounds like an estate agent, doesn't he? "Ignore the damp walls, darling, it's been raining. That motorway outside the window? Hardly anyone uses it."

Cameron and other ministers have made a feeble job of talking the story down. On Radio 4 Francis Maude (I expect Cruddas calls him "Frankie") even hid behind the Lib Dems – nothing new there – and said that even if the claims are true it wouldn't be possible to change policy "because we're in a coalition". Hmmm.

But let's not be too smug on a lovely spring morning. A major reason the politicians – Lib Dem (that fraudster's £2m has still not been returned) and Labour as well as greedy Tories – have to hire City wide boys to grovel to other City wide boys for cheques is that voters have repeatedly blocked the alternative routes.

As citizens we can either make donations to our party of choice, sanction their funding through a taxpayer-financed formula based on votes won or allow rich corporations, trades unions and individuals to stump up – as the Bernie Ecclestones and Henry Hooligans of this world seem happy to do so for gain, real or imagined. Some even do it for patriotic reasons: Mrs T was very good stroking that button.

Voters won't like any of the options, though they do expect highly professional political organisations and campaigns. Who's going to pay? Let's call it the tree-grown theory of money.

If it ever happens (talks have stalled for years) any reform would require tight spending caps to avoid American excesses which are largely the result of paid-and-pernicious TV advertising, which wise Europeans ban.

Barack Obama's fundraising in 2008 was pretty disgraceful, the small donations heavily outweighed by the large ones. He's at it again in 2012, but he's up against people who make Cruddas look like Mother Teresa's love child, so honest folk may shudder and avert their gaze.

Meanwhile Downing St is digging its heels in this morning against full disclosure of Sam and Dave's cheese on toast dinner guests and against an independent inquiry. By now I think Alastair Campbell might have cut his losses and surrendered on both points.